Ms LeBreton challenged the allegation: "The story that Senator Duffy spun in this place is not based in facts and it certainly leaves open to question what he was talking about and what he was thinking."

She said Mr Duffy spoke a "blatant falsehood" in order to avoid being expelled from the Senate over the expenses matter.

On Wednesday, Mr Harper denied involvement in the affair, telling the House of Commons he had been unaware of Mr Duffy's activities.

'Destroy my reputation'

Image caption
Senator Mike Duffy says the expenses were proper

Canadian senators are appointed by the governor general of Canada - the Queen's representative - on the advice of the prime minister. They typically join either the government caucus or the opposition caucus, or sit as independents.

Mr Duffy has been accused of seeking reimbursement for living expenses associated with a home in Ottawa, thought that, rather than a cottage in his home province of Prince Edward Island, was his primary residence.

He has argued the expense claims were within government guidelines for the reimbursement of senators who live outside Ottawa but must maintain a second home there.

Mr Duffy has said Mr Harper ordered him to repay the government after months of negative publicity. But he declined, arguing that to pay back money to which he was entitled would damage his reputation.

He then accused Mr Harper's office of "bribery, threats and extortion", and said Mr Harper threatened to force him from his Senate seat in order to cover up the row.

Mr Duffy's lawyer says the prime minister's office sought a way to repay the 90,000 Canadian dollars ($86,336; £53,292) it said Mr Duffy owed the taxpayers in order to put an end to the potentially damaging row. Mr Duffy reportedly agreed in order to avoid an audit.

Mr Harper's chief of staff Nigel Wright said in May that he provided the money to Mr Duffy, prompting an investigation by the Royal Canadian Mounted Police.

Mr Wright later resigned his post.

"Any assertion that I was in any way consulted or had any knowledge of Mr Wright's payment to Mr Duffy is categorically false," Mr Harper later told the media.